Stock pay-off apparatus have heretofore been made which brake rotation of a coil of continuous flexible stock in order to control the tension on the stock as it is withdrawn from the coil. Some stock pay-off apparatus utilize a substantially constant braking action on the coil and are objectionable because the tension on the exiting stock changes with the size of the coil. Other systems engage the stock as it exits from the coil to sense the tension in the stock and to operate a variable brake means accordingly. Such systems are not entirely satisfactory where the exiting stock might be damaged by contact with the tension sensing mechanism. Further, many stock tension control devices require external power, either electric, pneumatic or hydraulic, and this increases the expense and difficulty in installing and in moving the stock pay-off apparatus from place to place.
The present invention relates to a method and apparatus for controlling the stock tension as it is withdrawn from a coil.
An important object of this invention is to provide a method and apparatus for controlling the tension on flexible stock as it is withdrawn from a coil in which the exiting tension is maintained generally uniform independent of the diameter of the coil.
Another object of this invention is to provide an apparatus for controlling the tension on continuous flexible stock as it is withdrawn from a coil in which the tension on the exiting stock is sensed without contacting the stock after it exits from the coil.
Still another object of this invention is to provide a method and apparatus for controlling the tension on flexible stock as it is withdrawn from a coil which does not require any external power source for applying braking action to the coil.
Accordingly, the present invention provides a method for controlling the tension on continuous flexible stock as it is withdrawn from a coil in which the coil is supported for axial rotation about an axis extending transverse to the direction of stock withdrawal and for limited shifting movement lengthwise of the direction of stock withdrawal, the shifting movement of the coil in the direction of stock withdrawal being yieldably opposed with a generally uniform biasing force, and the rotation of the coil being variably braked as it shifts in the direction of stock withdrawal until the exiting tension on the stock substantially equals the biasing force that opposes the shifting of the coil in the direction of stock withdrawal.
The present invention further provides an apparatus for controlling the tension on the stock as it is withdrawn from a coil in which a carriage is mounted on a frame for movement relative thereto along a path generally lengthwise of the direction of stock withdrawal, a coil support is mounted on the carriage for rotation about an axis transverse to the path, biasing means yieldably urges the carriage along the path toward a retracted position, variable brake means controls rotation of the coil on the support, and mechanism operative in response to movement of the carriage along the path operates the variable brake means to increase and decrease the braking action as the carriage moves respectively toward and away from its retracted position. The carriage biasing means preferably applies a generally uniform force to urge the carriage toward its retracted position to thereby maintain a substantially constant tension on the stock as it is withdrawn from the coil.